Ask your model (or different people) to take a portrait and look for 10 different light situations. You may bring light with you, but you also could use available light to vary 10 times.
What comes to your mind if you think of different indirect and bounced light versus direct light, light situations?
Here are some ideas:
harsch light – soft light, warm light vs. colder light temperature, using diffusers and reflectors in 10 different ways, different angles of light, such as backlight and light from the side (or even from above and underneath), different sources of artificial light in the street, such as neon light ads, soft light early in the morning and warm flood of sunset light, high-key and low-key situations, one flash light with 10 different light modifiers…